SAMS PG MCQ’s •The answer is A. Polycythemia vera (PV) is a clonal disorder that involves a multipotent hematopoietic progenitor cell. Clinically, it is characterized by a proliferation of red blood cells (RBCs), granulocytes, and platelets. The precise etiology is unknown. Unlike chronic myelogenous leukemia, no consistent cytogenetic abnormality has been associated with the disorder. However, a mutation in the autoinhibitory, pseudokinase domain of the tyrosine kinase JAK2—that replaces valine with phenylalanine , causing constitutive activation of the kinase—appears to have a central role in the pathogenesis of PV. Erythropoiesis is regulated by the hormone erythropoietin. Hypoxia is the physiologic stimulus that increases the number of cells that produce erythropoietin. Erythropoietin may be elevated in patients with hormone-secreting tumors. Levels are usually “normal” in patients with hypoxic erythrocytosis. In PV, however, because erythrocytosis occurs independently of erythropoietin, levels of the hormone are usually low. Therefore, an elevated level is not consistent with the diagnosis. PV is a chronic, indolent disease with a low rate of transformation to acute leukemia, especially in the absence of treatment with radiation or hydroxyurea. Thrombotic complications are the main risk for PV and correlate with the erythrocytosis. Thrombocytosis, although sometimes prominent, does not correlate with the risk of thrombotic complications. Salicylates are useful in treating erythromelalgia but are not indicated in asymptomatic patients. There is no evidence that thrombotic risk is significantly lowered with their use in patients whose hematocrits are appropriately controlled with phlebotomy. Phlebotomy is the mainstay of treatment. Induction of a state of iron deficiency is critical to prevent a reexpansion of the RBC mass. Chemotherapeutics and other agents are useful in cases of symptomatic splenomegaly. Their use is limited by side effects, and there is a risk of leukemogenesis with hydroxyurea. •The answer is B. Cat bites are the most likely animal bites to lead to cellulitis because of deep inoculation and the frequent presence of Pasteurella multicoda. In an immunocompetent host, only cat bites warrant empirical antibiotics. Often the first dose is given parenterally. Ampicillin–sulbactam followed by oral amoxicillin– clavulanate is effective empirical therapy for cat bites. However, in an asplenic patient, a dog bite can lead to rapid overwhelming sepsis as a result of Capnocytophaga canimorsus bacteremia. These patients should be followed closely and given third-generation cephalosporins early in the course of infection. Empirical therapy should also be considered for dog bites in elderly adults, for deep bites, and for bites on the hand. •The answer is D. Although any valvular vegetation can embolize, vegetations located on the mitral valve and vegetations larger than 10 mm are greatest risk of embolizing. Of the answer choices, C, D, and E are large enough to increase the risk of embolization. However, only choice D demonstrates the risks of both size and location. Hematogenously seeded infection from an embolized vegetation may involve any organ but particularly affects those organs with the highest blood flow. They are seen in up to 50% of patients with endocarditis. Tricuspid lesions lead to pulmonary septic emboli, which are common in injection drug users. Mitral and aortic lesions can lead to embolic infections in the skin, spleen, kidneys, meninges, and skeletal system. A dreaded neurologic complication is mycotic aneurysm, focal dilations of arteries at points in the arterial wall that have been weakened by infection in the vasa vasorum or septic emboli, leading to hemorrhage. •The answer is B. Bullae (Latin for bubbles) are skin lesions that are greater than 5 mm and fluid filled. They may be regular or irregularly shaped and filled with serous or seropurulent fluid. Clostridium spp., including perfringens, may cause bullae through myonecrosis. Staphylococcus causes scalded skin syndrome through elaboration of the exfoliatin toxin from phage group II, particularly in neonates. Streptococcus pyogenes, the causative agent of impetigo, may cause bullae initially that progress to crusted lesions. MRSA may also cause impetigo. The halophilic Vibrio, including V. vulnificus, may cause an aggressive fasciitis with bullae formation. Patients with cirrhosis exposed to Gulf of Mexico or Atlantic waters (or ingestion of raw seafood from those waters) are at greatest risk. Infection with the dimorphic fungus, Sporothrix schenckii, presents with discrete crusted lesions resembling ringworm. Lesions may progress to ulcerate. Patients often have a history of working with soil or roses. •The answer is E. Although frequent nonbloody diarrheal illness is commonly associated with Clostridium difficile infection, other presentations are well described, including fever in 28% of cases, abdominal pain, and leukocytosis. Adynamic ileus is often seen with C. difficile infection, and leukocytosis in this condition should be a clue that C. difficile is at play. Recurrent infection after therapy has been described in 15% to 30% of cases. •The answer is A. Common causes of urethral discomfort and discharge in men include Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Ureaplasma urealyticum, Trichomonas vaginalis, and herpes simplex virus. Gardnerella spp. is the usual cause of bacterial vaginosis in women and is not a pathogen in men. •The answer is E. Probably because of its ubiquity and ability to stick to foreign surfaces, Staphylococcus epidermidis is the most common cause of infections of central nervous system shunts as well as an important cause of infections on artificial heart valves and orthopedic prostheses. Corynebacterium spp. (diphtheroids), similar to S. epidermidis, colonize the skin. When these organisms are isolated from cultures of shunts, it is often difficult to be sure if they are the cause of disease or simply contaminants. Leukocytosis in cerebrospinal fluid, consistent isolation of the same organism, and the character of a patient’s symptoms are all helpful in deciding whether treatment for infection is indicated. •The answer is D. Resistance to ampicillin and vancomycin is far more common in strains of Enterococcus faecium than E. faecalis. Linezolid and quinupristin–dalfopristin are approved by the U.S. Food and Drug Administration for the treatment of some vancomycin-resistant enterococci (VRE) infections. Linezolid is not bactericidal, and its use in severe endovascular infections has produced mixed results; therefore, it is recommended only as an alternative to other agents. Quinupristin–dalfopristin is not active against most E. faecalis isolates. Resistance to VRE strains of E. faecium is also emerging with increasing usage. Cephalosporins are generally inactive against enterococcal infections. •The answer is A. Neisseria meningitidis is an effective colonizer of the human nasopharynx, with asymptomatic infection rates of greater than 25% described in some series of adolescents and young adults and among residents of crowded communities. Despite the high rates of carriage among adolescents and young adults, only 10% of adults carry meningococci, and colonization is very rare in early childhood. Colonization should be considered the normal state of meningococcal infection. Meningeal pharyngitis rarely occurs. Meningococcal disease occurs when a virulent form of the organism invades a susceptible host. The most important bacterial virulence factor relates to the presence of the capsule. Unencapsulated forms of N. meningitides rarely cause disease. A nonblanching petechial or purpuric rash occurs in more than 80% of cases of meningococcal disease. Of patients with meningococcal disease, 30% to 50% present with meningitis, approximately 40% with meningitis plus septicemia, and 20% with septicemia alone. Patients with complement deficiency, who are at highest risk of developing meningococcal disease, may develop chronic meningitis. •The answer is B. The major reservoirs in the human body for anaerobic bacteria are the mouth, lower gastrointestinal tract, skin, and female genital tract. Generally, anaerobic infections occur proximal to these sites after the normal barrier (i.e., skin or mucous membrane) is disrupted. Thus, common infections resulting from these organisms are abdominal or lung abscess, periodontal infection, gynecologic infections such as bacterial vaginosis, and deep tissue infection. Properly obtained cultures in these circumstances generally grow a mixed population of anaerobes typical of the microenvironment of the original reservoir. •The answer is E. Sinoatrial dysfunction is often divided into intrinsic disease and extrinsic disease of the node. This is a critical distinction, as extrinsic causes are often reversible and pacemaker placement is not required. Drug toxicity is a common cause of extrinsic, reversible sinoatrial dysfunction, with common culprits including beta blockers, calcium channel blockers, lithium toxicity, narcotics, pentamidine, and clonidine. Hypothyroidism, sleep apnea, hypoxia, hypothermia, and increased intracranial pressure are all reversible forms of extrinsic dysfunction. Radiation therapy can result in permanent dysfunction of the node and therefore is an irreversible, or intrinsic, cause of sinoatrial node dysfunction. In symptomatic patients, pacemaker insertion may be indicated. •The answer is E. Patients at the highest risk for stroke associated with atrial fibrillation include those with a prior history of stroke, TIA, or embolism, and patients with hypertension, diabetes mellitus, congestive heart failure, rheumatic heart disease, LV dysfunction, and marked left atrial dilation of greater than 5.0 cm or age greater than 65 years. Anticoagulation should be strongly considered in these patients. Increased left atrial size is a risk factor for chronic atrial fibrillation. •The answer is E. Atrial septal defect (ASD) is a not uncommon simple congenital heart disease lesion that is often diagnosed in adults. Because of chronic left-to-right shunting of intracardiac blood, pulmonary arterial hypertension is a well-recognized common complication. With the development of pulmonary arterial hypertension, the potential for paradoxical embolization of either air or thrombotic material from the right atrium to the systemic circulation is increased. Similarly, with exertion in the context of pulmonary arterial hypertension and ASD, blood may shunt right to left, leading to systemic arterial oxygen desaturation. Atrial fibrillation or other supraventricular arrhyth- mias may occur, also as a result of atrial stretching with the lesion. While atherosclerosis and unstable angina may certainly occur in adults, is not a reported complication •The answer is A. Patients with severe aortic regurgitation will have a “water-hammer” pulse that collapses suddenly as arterial pressure rapidly falls during late systole and diastole, a so-called Corrigan’s pulse. Capillary pulsations seen in the nail bed in severe aortic regurgitation are named Quincke’s pulse. Traube’s sign, or a pistol shot sound, may be heard over the femoral arteries and Duroziez’s sign, with a to-and-fro murmur over the femoral artery, have also been described. Pulsus parvus et tardus is found in severe aortic stenosis. Pulsus bigeminus occurs when there is a shorter interval after a normal beat with a following low volume pulse, often with a premature ventricular beat. Pulsus paradoxus has been described with pericardial tamponade or severe obstructive lung disease. Pulsus alternans is alternating large and small volume pulses seen in severe heart failure. •The answer is E. Tricuspid regurgitation is most commonly caused by dilation of the tricuspid annulus due to right-ventricular enlargement of any cause. Any cause of left-ventricular failure that results in right-ventricular failure may lead to tricuspid regurgitation. Congenital heart diseases or pulmonary arterial hypertension leading to right- ventricular failure will dilate the tricuspid annulus. Inferior wall infarction may involve the right ventricle. Rheumatic heart disease may involve the tricuspid valve, although less commonly than the mitral valve. Infective endocarditis, particularly in IV drug users, will infect the tricuspid valve, causing vegetations and regurgitation. Other causes of tricuspid regurgitation include carcinoid heart disease, endomyocardial fibrosis, congenital defects of the atrioventricular canal, and right-ventricular pacemakers. •The answer is A. Bioprosthetic valves are made from human, porcine, or bovine tissue. The major advantage of a bioprosthetic valve is the low incidence of thromboembolic phenomena, particularly 3 months after implantation. Although in the immediate postoperative period some anticoagulation may occur, after 3 months there is no further need for anticoagulation or monitoring. The downside is the natural history and longevity of the bioprosthetic valve. Bioprosthetic valves tend to degenerate mechanically. Approximately 50% will need replacement at 15 years. Therefore, these valves are useful in patients with contraindications to anticoagulation, such as elderly patients with comorbidities and younger patients who desire to become pregnant. Elderly people may also be spared the need for repeat surgery, as their life span may be shorter than the natural history of the bioprosthesis. Mechanical valves offer superior durability. Hemodynamic parameters are improved with double-disk valves compared with single-disk or ball-and-chain valves. However, thrombogenicity is high and chronic anticoagulation is mandatory. Younger patients with no contraindications to anticoagulation may be better served by mechanical valve replacement. •The answer is E. Many infectious etiologies have been associated with the development of inflammatory myocarditis including viral agents (coxsackie, adenovirus, HIV, hepatitis C) and parasitic agents, with Chagas disease or T. cruzi being most prominent, but also toxoplasmosis. Additionally, bacterial etiologies like diphtheria, spirochetal disease like Borrelia burgdorferi, rickettsial disease, and fungal infections have been associated. •The answer is B. Pulsus paradoxus is an exaggeration of the normal phenomenon in which systolic blood pressure declines 10 mmHg or less with inspiration. Pulsus paradoxus is typically seen in patients with pericardial tamponade and in patients with severe obstructive lung disease (COPD, asthma). In pulsus paradoxus due to pericardial tamponade, the inspiratory systolic blood pressure decline is greater due to the tight incompressible pericardial sac. The right ventricle distends with inspiration, compressing the left ventricle and resulting in decreased systolic pulse pressure in the systemic circulation. In severe obstructive lung disease, the inspiratory decline of systolic blood pressure may be due to the markedly negative pleural pressure either causing left ventricular compression (due to increased RV venous return) or increased LV impedance to ejection (increased afterload). •The answer is C. Beck’s triad can be used to alert clinicians to the potential presence of cardiac tamponade. The principal features are hypotension, muffled or absent heart sounds, and elevated neck veins, often with prominent x-descent and absent y-descent. These are due to the failure of ventricular filling and limited cardiac output. Kussmaul’s sign is seen in restrictive cardiomyopathy and pericardial constriction, not tamponade. Friction rub may be seen in any condition associated with pericardial inflammation. •The answer is B. The functional residual capacity of the lung refers to the volume of air that remains in the lung following a normal tidal respiration. This volume of air represents the point at which the outward recoil of the chest wall is in equilibrium with the inward elastic recoil of the lungs. The lungs would remain at this volume if not for the actions of the respiratory muscles. The functional residual capacity is comprised of two lung volumes: the expiratory reserve volume and the residual volume. The expiratory reserve volume represents the additional volume of air that can be exhaled from the lungs when acted upon by the respiratory muscles of exhalation. The residual volume is the volume of air that remains in the lung following a complete exhalation and is determined by the closing pressure of the small airways.